Frank,I have NEVER seen such a thing with A/C 45's. I wonder if they're the new Chinese sizing??? Are you sure they are the right plug for the head. Some of the newer heads take the 5/8ths head plug and not the 13/16ths.

Frank,I have NEVER seen such a thing with A/C 45's. I wonder if they're the new Chinese sizing??? Are you sure they are the right plug for the head. Some of the newer heads take the 5/8ths head plug and not the 13/16ths.

Picked up a set of AC Delco R45TS, they are in and now to get the plug wires on and looking neat.

It's good to hear the R45TS plugs did the job for you and they are the right plugs for that cylinder head. I wasn't sure which heads you were using until I looked at the washers on the plugs in your picture. The washer compressed into a taper indicated that you had a tapered seat head.